Vessel occlusion device and method of using same

ABSTRACT

An improved embolic filter frame is provided. The filter frame provides enhanced longitudinal compliance, improved sealing, low profile delivery, and a short deployed length. The looped support struts have high “radial” stiffness with low “longitudinal” stiffness. When deployed, the frame exerts a relatively high stress onto a vessel wall to maintain an effective seal, yet remains longitudinally compliant. Minor displacements of the support wire or catheter are therefore not translated to the filter. The looped support struts elongate when tensioned and assume a compressed and essentially linear form. When the delivery catheter constraint is removed, the struts “snap open” and assume a looped configuration, exerting a high degree of force onto the vessel wall, creating an enhanced filter to vessel wall seal.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/677,734, filed Apr. 2, 2015 (now U.S. Pat. No. 9,642,691, issued May9, 2017), which is a continuation of U.S. patent application Ser. No.13/804,153, filed Mar. 14, 2013 (now U.S. Pat. No. 9,023,077, issued May5, 2015), which is a continuation of U.S. patent application Ser. No.13/555,543 filed Jul. 23, 2012 (now U.S. Pat. No. 9,023,076, issued May5, 2015), which is a continuation of U.S. patent application Ser. No.11/020,809 filed Dec. 22, 2004 (now U.S. Pat. No. 8,231,650, issued Jul.31, 2012) which is a continuation of U.S. patent application Ser. No.10/273,859 filed Oct. 17, 2002 (now abandoned).

FIELD OF THE INVENTION

The invention relates to embolic filter devices for placement in thevasculature and in particular, self-expanding frames used to supportembolic filter elements.

BACKGROUND OF THE INVENTION

Embolic protection is a concept of growing clinical importance directedat reducing the risk of embolic complications associated withinterventional (i.e., transcatheter) and surgical procedures. Intherapeutic vascular procedures, liberation of embolic debris (e.g.,thrombus, clot, atheromatous plaque, etc.) can obstruct perfusion of thedownstream vasculature, resulting in cellular ischemia and/or death. Thetherapeutic vascular procedures most commonly associated with adverseembolic complications include: carotid angioplasty with or withoutadjunctive stent placement; and revascularization of degeneratedsaphenous vein grafts. Additionally, percutaneous transluminal coronaryangioplasty (PTCA) with or without adjunctive stent placement, surgicalcoronary artery by-pass grafting, percutaneous renal arteryrevascularization, and endovascular aortic aneurysm repair have alsobeen associated with complications attributable to atheromatousembolization. The use of embolic protection devices to capture andremove embolic debris, consequently, may improve patient outcomes byreducing the incidence of embolic complications.

Embolic protection devices typically act as an intervening barrierbetween the source of the clot or plaque and the downstream vasculature.Numerous devices and methods of embolic protection have been usedadjunctively with percutaneous interventional procedures. Thesetechniques, although varied, have a number of desirable featuresincluding: intraluminal delivery; flexibility; trackability; smalldelivery profile to allow crossing of stenotic lesions; dimensionalcompatibility with conventional interventional implements; ability tominimize flow perturbations; thromboresistance; conformability of thebarrier to the entire luminal cross section (even if irregular); and ameans of safely removing the embolic protection device and trappedparticulates. There are two general strategies for achieving embolicprotection: techniques that employ occlusion balloons; and techniquesthat employ an embolic filter. The use of embolic filters is a desirablemeans of achieving embolic protection because they allow continuousperfusion of the vasculature downstream to the device.

Occlusion balloon techniques have been taught by the prior art andinvolve devices in which blood flow to the vasculature distal to thelesion is blocked by the inflation of an occlusive balloon positioneddownstream to the site of intervention. Following therapy, theintraluminal compartment between the lesion site and the occlusionballoon is aspirated to evacuate any thrombus or atheromatous debristhat may have been liberated during the interventional procedure. Theprinciple drawback of occlusion balloon techniques stems from the factthat during actuation, distal blood flow is completely inhibited, whichcan result in ischemic pain, distal stasis/thrombosis, and difficultieswith fluoroscopic visualization due to contrast wash-out through thetreated vascular segment.

A prior system described in U.S. Pat. No. 4,723,549 to Wholey, et al.combines a therapeutic catheter (e.g., angioplasty balloon) and integraldistal embolic filter. By incorporating a porous filter or embolusbarrier at the distal end of a catheter, such as an angioplasty ballooncatheter, particulates dislodged during an interventional procedure canbe trapped and removed by same therapeutic device responsible for theembolization. One known device includes a collapsible filter devicepositioned distal to a dilating balloon on the end of the ballooncatheter. The filter comprises a plurality of resilient ribs secured tocircumference of the catheter that extend axially toward the dilatingballoon. Filter material is secured to and between the ribs. The filterdeploys as a filter balloon is inflated to form a cup-shaped trap. Thefilter, however, does not necessarily seal around the interior vesselwall. Thus, particles can pass between the filter and the vessel wall.The device also lacks longitudinal compliance. Thus, inadvertentmovement of the catheter results in longitudinal translation of thefilter, which can cause damage to the vessel wall and liberate embolicdebris.

Other prior systems combine a guide wire and an embolic filter. Theembolic filters are incorporated directly into the distal end of a guidewire system for intravascular blood filtration. Given the current trendsin both surgical and interventional practice, these devices arepotentially the most versatile in their potential applications. Thesesystems are typified by a filter frame that is attached to a guide wirethat mechanically supports a porous filter element. The filter frame mayinclude radially oriented struts, one or more circular hoops, or apre-shaped basket configuration that deploys in the vessel. The filterelement is typically comprised of a polymeric or metallic mesh net,which is attached to the filter frame and/or guide wire. In operation,blood flowing through the vessel is forced through the mesh filterelement thereby capturing embolic material in the filter.

Early devices of this type are described in the art, for example in U.S.Pat. No. 5,695,519 to Summers, et al., and include a removableintravascular filter mounted on a hollow guide wire for entrapping andretaining emboli. The filter is deployable by manipulation of anactuating wire that extends from the filter into and through the hollowtube and out the proximal end. During positioning within a vessel, thefilter material is not fully constrained so that, as the device ispositioned through and past a clot, the filter material can potentiallysnag clot material creating freely floating emboli prior to deployment.The device also lacks longitudinal compliance.

Another example of a prior device, taught in U.S. Pat. No. 5,814,064 toDaniel, et al., uses an emboli capture device mounted on the distal endof a guide wire. The filter material is coupled to a distal portion ofthe guide wire and is expanded across the lumen of a vessel by a fluidactivated expandable member in communication with a lumen running thelength of the guide wire. During positioning, as the device is passedthrough and beyond the clot, filter material may interact with the clotto produce emboli. The device also lacks longitudinal compliance.

Another device, taught in U.S. Pat. No. 6,152,946 to Broome, et al.,which is adapted for deployment in a body vessel for collecting floatingdebris and emboli in a filter, includes a collapsible proximally taperedframe to support the filter between a collapsed insertion profile and anexpanded deployment profile. The tapered collapsible frame includes amouth that is sized to extend to the walls of the body vessel in theexpanded deployed profile and substantially longitudinal struts thatattach and tether the filter frame to the support wire. This device alsolacks substantial longitudinal compliance. This device has theadditional drawback of having an extended length due to thelongitudinally oriented strut configuration of the tapered frame. Thisextended length complicates the navigation and placement of the filterwithin tortuous anatomy.

A further example of an embolic filter system, found in PCT WO 98/33443,involves a filter material fixed to cables or spines of a central guidewire. A movable core or fibers inside the guide wire can be utilized totransition the cables or spines from approximately parallel to the guidewire to approximately perpendicular the guide wire. The filter, however,may not seal around the interior vessel wall. Thus, particles can passbetween the filter and the entire vessel wall. This umbrella-type deviceis shallow when deployed so that, as it is being closed for removal,particles have the potential to escape.

In summary, disadvantages associated with predicate devices include lackof longitudinal compliance, extended deployed length of the frame andassociated tethering elements, and inadequate apposition and sealingagainst a vessel wall. Without longitudinal compliance, inadvertentmovement of the filter catheter or support wire can displace thedeployed filter and damage a vessel wall and/or introgenic vasculartrauma, or, in extreme cases, result in the liberation of embolicdebris. An extended deployed length aggravates proper filter deploymentadjacent to vascular side branches or within tightly curved vessels.Inadequate filter apposition and sealing against a vessel wall has theundesirable effect of allowing emboli passage.

To ensure filter apposition and sealing against a vessel wall, withoutinducing undue vascular trauma, the radial force exerted by the filteragainst the vessel wall should be optimized. Typical methods used toincrease the radial force exerted by the filter include, for example,increasing the cross-sectional area (moment of inertia and therefore thestiffness) of the filter support frame and in particular the tetheringelements of the frame. Enhanced radial force can also be achieved byincorporating additional support members or by enlarging the “relaxed”or deployed diameter of the filter frame relative to the diameter of thevessel into which it is deployed. These methods typically have theundesirable side effects of degrading the longitudinal compliance,adding to the compressed delivery profile, and, in some cases,increasing the deployed length. Some methods used to increase the radialforce (for example, stiffer support frames) have the additional drawbackof requiring thicker-walled, larger profile, delivery catheters. Toaccommodate the increased pressure exerted by the stiff frame(constrained within the delivery catheter) a commensurately thickercatheter wall is required, compromising the delivery profile.

SUMMARY OF INVENTION

The present invention is an improved embolic filter frame having loopedsupport struts. The frame configuration of the present inventionprovides enhanced longitudinal compliance, improved sealing against avessel wall, low profile delivery, and a short deployed length occupiedby the frame and tethering elements.

To improve the apposition and sealing against a vessel wall, the presentinvention incorporates a filter support frame having “looped” supportstruts. The “looped” strut configuration enhances the radial forceimparted onto a vessel wall without entailing the undesirable sideeffects previously described. The looped strut configuration alsofacilitates filter frame opposition when deployed in tortuous vascularanatomies. When in a tensioned or compressed delivery state, the loopedsupport struts of the present invention assume an essentiallylongitudinal configuration and impart minimal radial force onto thecatheter wall. The thickness of the catheter wall or radial constraintcan therefore be minimized to increase flexibility, decrease thecatheter profile, and enhance insertion trackabilty. During thedeployment procedure, the looped support struts assume a loopedconfiguration. Once in the deployed, looped configuration, the supportstruts exert a high degree of radial force onto the vessel wall,enhancing apposition and sealing. The looped support struts also providea high degree of longitudinal compliance relative to conventionaldesigns. In addition, the full length of the looped support struts ispositioned very close to the filter element, which minimizes the overalldeployed length of the filter media support element.

Among the important benefits of the present invention is that thedeployed device of the present invention exhibits a low degree of“longitudinal” stiffness. Thus, in the deployed state, the deviceremains limp and compliant in the longitudinal direction. Consequently,minor longitudinal displacements of the support wire or catheter are nottranslated to the filter frame and vessel wall during guide wiremanipulation.

Another beneficial feature of the present invention is that the loopedstruts and the central collar connecting the support struts to thesupport wire of the present invention are positioned essentially withinthe plane of the filter opening and, if desired, can even be positionedwithin the filter frame element itself. This improves the utility of theembolic filter of the present invention by reducing the overall deployedlength of the filter support frame and allowing the filter to bedeployed very close to the treatment site.

These enhanced features and other attributes of the embolic filter ofthe present invention are better understood through review of thefollowing specification.

BRIEF DESCRIPTION OF DRAWINGS

The operation of the present invention should become apparent from thefollowing description when considered in conjunction with theaccompanying drawings, in which:

FIG. 1 is a three-quarter isometric view of an embolic filter of thepresent invention, with a support frame having three looped supportstruts.

FIG. 2 is an enlarged partial view of the support frame of FIG. 1.

FIG. 3A is an end view of the embolic filter of FIG. 1, depicting thesupport frame assuming an unconstrained diameter.

FIG. 3B is a partial side-view of a looped support strut of the presentinvention, defining a bend angle in the support strut.

FIG. 3C is a partial side-view of a looped support strut of the presentinvention, defining an “s” shape in the support strut.

FIG. 4 is a three-quarter isometric view of an embolic filter of thepresent invention as deployed into a vessel.

FIG. 5A is a partial three-quarter isometric view of an embolic filterof the present invention, defining the filter opening planes.

FIGS. 5B through 5D are side views of an embolic filter of the presentinvention illustrating deployed diameters and various types of offsetstrut attachment points.

FIGS. 6A and 6B are side views of an embolic filter of the presentinvention defining deployed diameters and overall lengths.

FIGS. 6C and 6D are side views of an embolic filter frame of the presentinvention, defining deployed diameters and lengths.

FIGS. 7A through 7C are side views of an embolic filter of the presentinvention, showing various stages of tensioning and elongation.

FIG. 7D is a side view of an embolic filter of the present inventionconstrained within a sheath.

FIGS. 8A and 8B are, respectively, an end view and a side view of oneembodiment of an embolic filter of the present invention, showing threesupport struts with loops, as viewed along two orthogonal axes.

FIGS. 9A and 9B are, respectively, an end view and a side view of afurther embodiment of an embolic filter of the present invention,showing three support struts with loops, as viewed along two orthogonalaxes.

FIGS. 10A and 10B are, respectively, an end view and a side view ofanother embodiment of an embolic filter of the present invention,showing three support struts with loops, as viewed along two orthogonalaxes.

FIGS. 11A and 11B are, respectively, an end view and a side view ofstill another embodiment of an embolic filter of the present invention,showing three support struts with loops, as viewed along two orthogonalaxes.

FIGS. 12A through 12F are end views of embolic filters embodiments ofthe present invention, showing, respectively, three, four, five, six,seven, and eight looped support struts.

FIG. 13 is a longitudinal cross-section view of an embolic filter frameof the present invention, depicting an enhanced radial force caused byvessel wall compression.

FIG. 14 is a side view of an embolic filter device of the presentinvention wherein the frame includes a truncated filter membrane supportportion.

FIG. 15 is a three-quarter isometric view of a cut-out precursor tubeused to fabricate a six-strut embolic filter frame of the presentinvention according to Example 1.

FIG. 16 is a three-quarter isometric view of the precursor tube of FIG.15 that has been expanded to form a six-strut embolic filter frame ofthe present invention.

FIG. 17 is a side view of an expanded and inverted precursor tube usedto fabricate a six-strut embolic filter frame of the present inventionaccording to Example 1.

FIGS. 18A through 18C are longitudinal cross-section views of anotherembodiment of an embolic filter device of the present invention having aslidable attachment between the filter frame and the support wire.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of the present invention is shown in FIG. 1. Shown isan unconstrained, non-tensioned embolic filter assembly 30 of thepresent invention. The filter assembly 30 comprises a frame 31 havingtwo distinct portions: a filter support portion 32 and a series oflooped struts or tethers 34. Each looped strut 34 is affixed to acentral collar 46, which is then attached to a support wire 36 atattachment point 38. Multiple struts 34 emanate radially outward and areattached to the frame's filter support portion 32. Attached to thefilter support portion 32 is a filter element 40. Also shown is alongitudinal axis 42, which is essentially coincident with the supportwire 36.

Embolic filter frames of the present invention can have 2, 3, 4, 5, 6,7, 8 or more looped support struts. The number of support struts caneffect the profile and shape of the filter membrane opening 60. Forexample, the frame configuration in FIG. 1, showing only three supportstruts for clarity, typically results in a filter opening having three“scallops” 41 which follow the profile of the filter support portion 32.By incorporating additional support struts, the magnitude or size ofeach scallop 41 is reduced and the filter opening will more closelyapproximate a circle within a plane. In a preferred embodiment, sixlooped support struts are incorporated into a frame of the presentinvention. The filter element may be trimmed to match the contour of thescallops so to avoid deflecting or disrupting fluid flow or potentiallyallowing inadvertent passage of emboli.

The distal end 35 of the filter element is preferably provided with aslidable attachment around the support wire 36 so as to allow the filterelement to change position relative to the support wire 36 betweencompacted and deployed dimensions. Additionally, a slidable interfacebetween the distal end 35 and the support element allows the filterelement to remain fully extended in the vessel at all times, even whenthe filter assembly is undergoing longitudinal compliance, as describedherein. Alternatively or additionally, the filter element may be formedfrom an elastic material that can accommodate different distal endpositions relative to the position of the filter frame.

Shown in FIG. 2 is an enlarged view of the unconstrained looped supportstruts of an embolic filter 30 of the present invention. Shown is aframe 31 having filter support portions 32 and three looped supportstruts 34. Also shown are support wire 36, central collar 46, collar tosupport wire attachment point 38, and a filter element 40. Shown is apreferred embodiment in which the looped support struts 34 areessentially “s” shaped.

FIG. 3A illustrates the unconstrained embolic filter assembly 30 fromFIGS. 1 and 2. Shown are three preferred s-shaped, looped support struts34 extending radially from the central collar 46. The support struts 34extend from and are attached to a filter support portion 32. Attached tothe filter support portion 32 is a filter element 40. The embolic filter30, shown in an unconstrained state, has an unconstrained diameter 44.

Referring again to FIG. 2, shown are three looped support struts 34,support wire 36, central collar 46, collar to support wire attachmentpoint 38, and a filter element 40. It will be noted that attachmentpoint 38 may comprise a rigidly secure fixation point between thesupport wire 36 and the centered collar 46, or it may comprise aslideable interface between the support wire 36 and central collar 46;thereby decoupling longitudinal or rotational motion of the support wirefrom the filter frame. The support struts 34 extend radially and areattached to a filter support portion 32. Attached to the filter supportportion 32 is a filter element 40. A “filter support portion” is definedas that portion of a filter frame that is at least partially attached toa filter element 40. A “support strut” is defined as that portion of afilter frame that supports the filter support portion and generally isnot attached directly to the filter element 40.

A “looped support strut” is further illustrated in FIG. 3B. Shown is thesupport strut 34 unattached to a filter element and constrained about asupport wire or longitudinal axis 42. A reference axis 47, drawn throughthe support strut 34 as shown, approximates the magnitude of a bend orloop in the support strut. The axis 47 defines an angle 48 relative tothe longitudinal axis 42 (also shown is a reference axis 49 whichdefines a 90 degree angle relative to the longitudinal axis 42). Shownis a looped support strut angle 48, which is greater than 90 degrees,relative to the longitudinal axis 42. A “looped strut” is thereforedefined as a filter frame support strut, having a portion unattached toa filter element, wherein the strut has at least one bend equal to orgreater than 90 degrees along the unattached portion. The looped anglecan be viewed and measured about any axis.

A looped, embolic filter frame support strut having an “s” shape isdepicted in FIG. 3C. Shown is the support strut 34 unattached to afilter element and constrained about a longitudinal axis 42. Also shownis an axis 37, which is parallel to the longitudinal axis 42. Areference axis 47, drawn through the support strut 34, as shown,approximates the magnitude of the bends or loops in the support strut.The axis 47 defines angles 48 relative to the longitudinal axis 42.Shown are two opposite bend angles 48, each of at least about 90degrees. A “support strut having an ‘s’ shape” is defined as a filterframe support strut having a portion unattached to a filter element,wherein the strut has at least two opposite bends greater than about 90degrees along the unattached portion. The angles 48 can be viewed andmeasured about any axis.

The aspect of “longitudinal compliance” is further clarified in FIG. 4.Shown is an embolic filter assembly 30 of the present invention deployedwithin a compliant vessel 50 (shown in longitudinal cross-section). Thevessel 50 defines an inner diameter which is slightly smaller, forexample approximately 90%, than the unconstrained diameter of thedevice. This is shown as diameter 44 in FIG. 3A. The “under-sized”vessel therefore imparts a radial constraint to the deployed filter,which prevents the filter from expanding to a full, unconstraineddiameter. In this process, an interference fit between the filter andvessel wall is achieved. The looped support struts 34 when constrainedby a vessel therefore exert a radial or expansive force 52 onto thevessel wall 50, forming a seal region 54. This radial, expansive force52 can also be referred to as the “hoop stress” or “radial force”applied to the vessel wall.

As the term “unconstrained diameter” is used herein, it is intended todescribe the device of the present invention as it self-deploys on atabletop. In this form it is both unconstrained and untensioned. Thisstate is also referred to herein as being “not in tension” or in a“non-tensioned” state.

Once deployed, the support wire 36, when rigidly fixed at or about thecentral collar, can be slightly displaced along the longitudinal axis 42in directions 56 or 58 without significantly disrupting or translatingto the seal region 54. The looped support struts 34 therefore provide adegree of “longitudinal compliance” which effectively isolates thefilter element from small support wire displacements. Devices of thepresent invention having unconstrained diameters of about 6 mm (0.24″)can tolerate support wire displacements in directions 56 or 58 of about+/−0.8 mm (+/−0.03″) or more, without causing a significant disruptionor translation to the seal region 54. The support wire therefore has a“maximum total displacement” before causing a disruption to the sealregion 54.

Longitudinal compliance can be alternately expressed as a ratio ofunconstrained diameter divided by the maximum total support wiredisplacement when rigidly fixed to the support wire (without disruptingor translating the seal region against the vessel wall). To determinethis ratio, a device of the present invention can be deployed within atransparent elastic tube having a diameter of about 80% of the filter'sunconstrained diameter. The maximum total support wire displacement(without disrupting or moving the seal region) can then be approximated.Devices of the present invention display ratios of unconstraineddiameter divided by the maximum total displacement of the support wireof about 6 or less. Preferably, the embolic filter of the presentinvention has a ratio of unconstrained diameter to maximum support wiredisplacement of about 5, about 4, about 3, about 2.5, about 2, about1.5, about 1.2, or about 1.

A relatively easy test to quantify longitudinal compliance in thepresent invention is to deploy the filter apparatus within a siliconetube (such as that available from JAMAK Healthcare Technologies,Weatherford, Tex.) having a thin wall thickness of approximately 0.25 mm(0.01″) and having an internal diameter of approximately 80% that of theunconstrained filter apparatus. It should be noted that the use of an80% constrained diameter is preferred since a 20% interference fitbetween the device and the vessel will prevent device migration andprovide adequate sealing. Once deployed and at body temperature(approximately 37° C.), the support wire to which the apparatus isattached may be longitudinally manipulated. The maximum distance thesupport wire can be displaced (in a longitudinal direction) withoutmoving the filter frame in relation to the silicone tubing is recordedas “longitudinal compliance.”

The present invention also has the beneficial feature of a shortdeployed length, as depicted in FIGS. 5A through 5D. The short deployedlength of the present invention is a result of the looped struts and thecentral collar connecting the support struts to the support wire beingpositioned essentially within the plane of the filter opening. Dependingupon the demands of particular applications, the looped struts can beengineered to deploy to be directly within the plane of the opening tothe filter element, slightly upstream of the opening, or even slightlydownstream of the opening so as to orient within the filter frameelement itself. Shown in FIG. 5A is an embolic filter 30 of the presentinvention in an unconstrained state having a proximal end 43 and adistal end 45. The filter element 40 has a filter “opening” 60, whichdefines a plane having an x-axis 62 and an y-axis 64. For filteropenings with scallops 41, the opening axis 62 and 64 are positioned atthe most proximal ends of the scallops 41. The opening plane shown isorthogonal to the support wire 36 and the longitudinal axis 42. The twoaxes 62, 64 therefore define the plane of the filter opening 60. Loopedstruts 34, of the present invention are joined onto a central collar 46,which is attached to the support wire 36 at attachment point 38 viaeither rigidly fixed or slidable means.

Shown in FIG. 5B is a filter element 40 having a filter opening 60, any-axis 64, and a longitudinal axis 42. The axis 64 is an “edge-view” ofthe plane of the filter opening. Axes 42 and 64 intersect at point 70.Point 70 is therefore on the plane of the filter opening. For clarity, apoint or location on the longitudinal axis 42 is considered to be“offset distally” from the plane of the filter opening if the point lieswithin the filter element in the longitudinal direction labeled 72.Conversely, a point or location on the longitudinal axis 42 isconsidered to be “offset proximally” from the plane of the filteropening if the point lies outside of the filter element in thelongitudinal direction labeled 74.

FIG. 5C illustrates a looped support strut 34 and central collar 46 ofthe present invention having a support wire attachment point 38 which isrigidly fixed to the support wire and off-set distally from the plane ofthe filter opening 64. Shown is a support wire attachment point 38positioned inside the filter element 40 in the distal direction 72. Themagnitude of the attachment point offset is shown as element 80.

FIG. 5D illustrates a looped support strut 34 and central collar 46 ofthe present invention having a support wire attachment point 38 which isrigidly fixed to the support wire and off-set proximally from the planeof the filter opening 64. Shown is a support wire attachment point 38,positioned outside of the filter element 40, in the proximal direction74. The magnitude of the attachment point offset is shown as item 82.

The relative magnitude of any off-set, along with the direction of theoff-set between a support wire attachment point and the plane of thefilter opening 64, can be expressed by an “offset ratio” of the strutattachment point off-set divided by the unconstrained diameter 44. Forexample, a filter having a strut attachment point offset of 4 mm and anunconstrained diameter of 10 mm, would have a ratio of 0.4. This ratiocan be applied to strut to support wire attachment points that areoffset distally or proximally to the plane of the filter opening. Aratio of “zero” would reflect no offset, or in other words an attachmentpoint lying in the plane of the filter opening.

Embolic filters of the present invention can have distally offset ratios(of the attachment point off-set divided the unconstrained diameter)ranging from about 0 to about 1, with a preferred range of about 0 toabout 0.7, with a most preferred range of about 0.2 to about 0.5. Thesedistally offset ratios reflect strut/collar to support wire attachmentspositioned within the filter element. Similarly, embolic filter of thepresent invention can have proximally offset ratios, reflectingstrut/collar to support wire attachments positioned outside of thefilter element. In these configurations, embolic filters of the presentinvention can have offset ratios (attachment point offset divided by theunconstrained diameter) ranging from about 0 to about 1.

Devices of the present invention can be configured to have a strut tocentral collar attachment points that are significantly different thanthe central collar to support wire attachment points. For theseconfigurations, both attachment points are then approximated by a pointon the support wire that is in closest proximity to the strut.

The looped support struts of the present invention allow a shortdeployed length that enhances navigation within tortuous vessels andallows deployment near vascular side-branches. To quantify as having theaspect of “short deployed length,” a device should be defined by atleast one of the five ratios defined below.

The deployed length of a filter can be expressed by a first ratio of thedeployed length divided by the unconstrained diameter of the filter.Shown in

FIG. 6A is an embolic filter 30 of the present invention having a filterelement 40, looped struts 34, strut/collar to support wire attachmentpoint 38 (lying outside of the filter element), and a unconstraineddiameter 44. Shown is a deployed length 84, which includes the loopedstruts 34 and the attachment point 38.

Shown in FIG. 6B is an embolic filter 30 of the present invention havinga filter element 40, looped struts 34 a, strut/collar to support wireattachment point 38 (lying within the filter element), and aunconstrained diameter 44. Shown is a deployed length 86, which isreferenced from the opposing ends of the filter element, and does notinclude the looped struts 34 a or the attachment point 38.

Embolic filters of the present invention can have ratios of the deployedlength 84, 86 divided by the filter unconstrained diameter 44, rangingfrom about 0.5 to about 7, with a preferred range of about 1 to about 5,with a most preferred range of about 2 to about 4.

A similar expression of a filter deployed length or footprint is asecond ratio of the deployed length of the frame (not including a filterelement) divided by the frame unconstrained diameter. Shown in FIG. 6Cis an embolic filter frame of the present invention having filtersupport portions 32 and looped struts 34, strut/collar to support wireattachment point 38 (lying outside of the filter element 40), and aunconstrained frame diameter 44. Shown is a frame deployed length 87,which does not include the filter element 40.

Shown in FIG. 6D is an embolic filter frame of the present inventionhaving filter support portions 32 and looped struts 34, strut/collar tosupport wire attachment point 38 (lying within the filter element 40),and a unconstrained diameter 44. Shown is a frame deployed length 88,which does not include the filter element 40.

Embolic filters of the present invention can have ratios of the framedeployed length 87, 88 divided by the frame unconstrained diameter 44,ranging from about 0.1 to about 7, with a preferred range of about 0.3to about 2, with a most preferred range of about 0.5 to about 1.

Additional benefits of the looped struts of the present invention relateto the delivery aspects of the embolic filter as shown in FIGS. 7Athrough 7D. The looped support struts of the present invention whentensioned elongate and assume a compacted and essentially linear form.While constrained in this linear state by a delivery catheter or otherconstraint means, the support struts exert relatively little force ontothe radial constraint means, which permits the radial constraint meansto be very thin and/or delicate. The overall delivery profile andstiffness are therefore reduced over those required for prior embolicfilter devices.

When the delivery catheter constraint is removed during deployment, thestruts of the present invention spontaneously open and assume a loopedconfiguration, which exert a high degree of force onto the vessel wall,creating an enhanced filter to vessel wall seal. Shown in FIG. 7A is anembolic filter 30 of the present invention having looped struts 34attached to a central collar 46. The central collar is attached to asupport wire 36. The support struts emanate radially outward and areintegral to (or joined to) a frame having a filter support portion 32. Afilter element 40 is attached to the filter support portion 32.

When tension 90 is applied to the support wire 36 and filter element 40,the looped struts 34 elastically deform to the configuration shown inFIG. 7B. As further tension 90 is applied, the embolic filter 30 and thelooped struts 34 continue to elongate until the looped struts assume anessentially linear or straight form as shown in FIG. 7C. While in thiselongated state, the embolic filter 30 can be inserted into a deliverycatheter or withdrawn into a sheath. Shown in FIG. 7D is an elongatedembolic filter 30 of the present invention having looped struts 34 in anessentially linear configuration constrained in a deliver catheter 92.The low force applied to the delivery catheter by the elongated loopedstrut facilitates use of a relatively thin catheter wall 94. When theconstraining delivery catheter is removed during filter deployment, thelooped struts of the present invention spontaneously open and assume theconfiguration shown in FIGS. 4 and 7A, either spontaneously or throughmanipulation of the support wire and/or delivery catheter.

During delivery within a vessel, struts 34 of an embolic filter of thepresent invention are constrained in an “essentially linear” form, asshown in FIG. 7D. While in this essentially linear form, the centralsupport collar 46 (or strut to support wire attachment point 38) ispositioned outside of the filter element 40. The central support collar46 is also separated from the filter element 40 by the elongated andessentially linear support struts 34. Once properly deployed, however,the central support collar 46 (or strut to support wire attachment point38) lies within the filter element 40, as shown in FIG. 7A. The centralsupport collar 46 (or strut to support wire attachment point 38)therefore moves or translates relative to the filter element duringdeployment. Typical filters of the present invention undergo a relativetranslation (support collar to filter element) equal to at least ½ ofthe length of the constrained filter element 96 (as is shown in FIG.7D).

Also shown in FIG. 7D is a total constrained delivery length 97 of anembolic filter of the present invention. Embolic filters of the presentinvention can have a third ratio of the total constrained deliverylength 97 divided by the unconstrained length. For the presentinvention, this third ratio may be about 1, about 2, about 2.5, about 3,about 3.5, or greater. The unconstrained length is defined by length 84(FIG. 6A) or by length 86 (FIG. 6B).

Similarly, embolic filters of the present invention can have a fourthratio of the total constrained frame delivery length 98 divided by theunconstrained frame length. For the present invention, this fourth ratiomay be about 2, about 2.5, about 3, about 3.5, or greater. Theunconstrained frame length is defined by length 87 (FIG. 6C) or bylength 88 (FIG. 6D).

A fifth ratio relating to the short deployed length is the strutconstrained delivery length divided by the strut unconstrained deployedlength. The strut constrained delivery length is defined as the lengthof a strut portion 34 of the frame, not including the filter supportportion 32, as shown in FIG. 7D. The strut constrained delivery lengthis therefore a portion of the total frame length 98 in FIG. 7D. Thestrut unconstrained length is defined as the length of a unconstrainedstrut 34 a as shown in FIGS. 6C and 6D, not including the length of afilter support portion 32. Filter frames of the present invention canhave ratios of the strut constrained delivery length divided by thestrut unconstrained deployed length of about 2, of about 3, of about 4,of about 5, of about 6, or about 7, or more. Filter frames of thepresent invention preferably have ratios of the strut constraineddelivery length divided by the strut unconstrained deployed length ofabout 3, of about 3.5, of about 4, of about 4.5, or about 5 or more.Most preferred ratios of strut constrained delivery length divided bythe strut unconstrained deployed length are about 3, about 3.3, of about3.6, or about 4, or more.

Embolic filters of the present invention can be produced using a varietyof common methods and processes. For example, an embolic filter framewith looped struts can be fabricated from any biocompatible materialhaving adequate resilience and stiffness. For example, nitinol,stainless steel, titanium, and polymers may be employed as applicablematerials. A precursor frame having looped struts may be fabricated in aplanar sheet form and rolled and attached to itself to form a frame ofthe present invention. Alternately, a cylindrical tube can be cut andexpanded or cut and compressed to form a frame of the present invention.Cutting processes can include lasers, stampings, etching, mill-cutting,water-jets, electrical discharge machining, or any other suitableprocess.

Filter elements or members, used in conjunction with the looped strutsof the present invention, can be produced using a variety of commonmaterials, methods and processes. Suitable biocompatible materialsinclude, but are not limited to, metallic foils or meshes, or sheets ormeshes formed from various polymers, including fluoropolymers such aspolytetrafluoroethylene. Filter members can be molded, cast, formed, orotherwise fabricated by joining various suitable materials.

FIGS. 8 through 12 illustrate (but do not limit) various alternateembodiments of looped struts of the present invention. Shown in FIGS. 8Aand 8B is an embolic filter 30 having a preferred looped strutconfiguration 34. A preferred strut 34 of the present invention can havea looped shape or profile when viewed along two orthogonal axes. Thestruts 34 therefore project a looped configuration in two orthogonalviews.

Alternate strut configurations of the present invention can have loopedshapes when viewed along different combinations of axes or along asingle axis. For example, shown in FIGS. 9A and 9B are similar views tothose of 8A and 8B, showing an alternate looped strut configurationwherein the alternate strut 34 has an essentially looped shape only whenviewed along a single axis. Shown is a strut 34 having a looped shape inan end view (FIG. 9A) and an essentially linear shape in a side view(FIG. 9B).

Alternately, a strut of the present invention can have an essentiallylinear shape when viewed on end, while having a looped shape whenviewed, for example from the side. This configuration is illustrated inFIGS. 10A and 10B, which show an alternate strut 34 having anessentially linear shape when viewed from the end (FIG. 10A), whilehaving a looped configuration when viewed from the side (FIG. 10B).

Looped support struts of the present invention can be configured withbends greater than about 90 degrees (as defined by FIG. 3C), greaterthan about 120 degrees, greater than about 180 degrees, greater thanabout 240 degrees, or more. For example, a looped strut of the presentinvention having a bend greater than about 200 degrees is depicted inFIG. 11A. Shown is an embolic filter 30 having looped support struts 34with “spiral” bends of about 200 degrees or more. The struts 34 alsohave a looped configuration when viewed from another axis, in this casea side view, as shown in FIG. 11B. Looped support struts of the presentinvention can therefore have different “loop” configurations whenprojected onto different viewing planes.

Shown in all FIGS. 8 through 11 are embolic filters having three, loopedsupport struts with support wire attachment points 38 and centralsupport collars 46, lying essentially within the filter element, aspreviously described in FIGS. 5A and 5B. Embolic filter frames of thepresent invention can have 2, 3, 4, 5, 6, 7, 8, or more looped supportstruts. Various multiple strut configurations are depicted in FIGS. 12Athrough 12F.

FIG. 12A shows an end view of an embolic filter of the present inventionhaving 3 looped struts 34.

FIG. 12B shows an end view of an embolic filter of the present inventionhaving 4 looped struts 34.

FIG. 12C shows an end view of an embolic filter of the present inventionhaving 5 looped struts 34.

FIG. 12D shows an end view of an embolic filter of the present inventionhaving 6 looped struts 34.

FIG. 12E shows an end view of an embolic filter of the present inventionhaving 7 looped struts 34.

FIG. 12F shows an end view of an embolic filter of the present inventionhaving 8 looped struts 34.

An additional functional aspect of embolic filter frames of the presentinvention is shown in FIG. 13. Shown is an embolic filter 30 havinglooped support struts 34, filter element 40 attached to the filterelement support 32, central collar 46, and support wire 36. Whendeployed within an undersized vessel (that is, a vessel that isundersized relative to the filter's relaxed fully deployed diameter), acompressive load 100 is applied to the frame, which counteracts theradial force applied by the frame to the vessel. The compressive load100 causes a frame portion, in this case the filter element supportportion 32, to deflect outwardly, as shown by item 102. The deflection102 can improve the sealing between the filter element 40 and the vesselwall, further reducing the advertent passage of emboli. The additionalloading onto the vessel wall can also reduce the possibility of“vascular trauma” caused by relative motion between the filter and thevessel, and opposition when deployed in curved vascular segments.

Shown in FIG. 14 is an alternate configuration of a frame having loopedstruts 34 and having a simplified filter support portion (in contrast tothe elongated filter support portions 32 shown in FIG. 2). Shown are asupport wire 36 and a filter element 40 attached directly to the ends ofthe six looped support struts 34 of the present invention. The supportstruts 34 attach to the filter element 40 at attachment points 103. Itshould be appreciated that the length and shape of the struts 34 in thisembodiment may be varied to accommodate bonding of struts 34 todifferent points on the filter element or to bond the filter element 40along a partial length of the struts 34.

An additional feature of a filter frame of the present invention relatesto the looped strut “spontaneous” transformation from a constrainedlinear state to a “locked” and inverted state, similar to that of“locking pliers” or an “off-center locking clamp”. Once inverted, thelooped struts maintain a stable, short length, looped configuration andmust be tensioned to revert back to the constrained linear state.

The term “support wire”, as referred to and relating to the presentinvention, (for example, element 36 in FIG. 1) can include a solid orhollow support wire or can include any other tubular article with atleast one continuous lumen running therethrough. A suitable support wirefor use with the present invention may include, but is not limited to, aguide wire.

Filters of the present invention can be configured for deployment withina variety of articles, including, but not limited to, filteringapplications within animal vessels, catheters, pipes, ducts, fluidconduits, tubes, hoses, material transfer conduits, storage containers,pumps, valves and other fluid containers. Filterable fluids includegasses, liquids, plasma and flowable solids or particulate mixtures.Fluids can flow across the filters of the present invention, or thefilters can be dragged or otherwise transported through a fluid. Filtersof the present invention are not limited to generally circular profiles(when viewed on end) and can have, when deployed an oval, triangular,square, polygon, or other profile. Filters of the present invention canalso be combined, “ganged,” or used in conjunction with other devicessuch as diagnostic, visualization, therapeutic instruments, or otherfilters. The strut configurations of the present invention can also beincorporated into non-filtering devices, such as vessel occluders,indwelling diagnostic instruments, therapeutic instruments, orvisualization devices.

Without intending to limit the scope of the present invention, thedevice and the method of production of the present invention may bebetter understood by referring to the following example.

EXAMPLE 1

As shown in FIG. 15, a 0.9 mm nitinol tube 104, with a wall thickness ofapproximately 0.09 mm (obtained from SMA Inc, San Jose, Calif.) waslaser cut by Laserage Technologies Inc, Waukegan, Ill., to form a frameconfiguration of a single, undulating, integral, 6 apex ring. The frameincluded radiopaque marker housings 106 at each distal apex and tetheror strut elements 34 extending from each proximal apex 108 andconverging at the opposite end in a “collar” 46 of uncut parentmaterial. This frame was then lightly grit blasted at 30 psi with20-micron silicon carbide media in a grit blasting machine (Model MB1000available from Comco Inc, Burbank, Calif.). The frame was then gentlyslid up a tapered mandrel until it achieved a functional size ofapproximately 6 mm.

The frame and mandrel were then subjected to an initial thermaltreatment to set the geometry in an initial, tapered (conical)configuration in an air convection oven (Carbolite Corporation,Sheffield, England). The frame was quenched in ambient temperature waterand removed from the mandrel, resulting in a non-inverted frame.

Shown in FIG. 16 is the non-inverted frame 110 having support struts 34,a central collar 46, apexes 108, and radiopaque marker housings 106. Theframe portion distal to the apexes 108 form a filter element supportportion 32. The frame was then placed on a second mandrel, designed toconstrain the outside of the frame while allowing the inversion of thetether elements back upon themselves. Once constrained in the properconfiguration, the tooling and frame were subjected to a second thermaltreatment to set the final frame geometry and to set the nitinoltransition to an appropriate temperature. The resulting inverted frameis depicted in FIG. 17.

Shown in FIG. 17 is an inverted frame 112 having six looped supportstruts 34 a, apexes 108, radiopaque housings 106, and an integralcentral collar 46. The frame portion distal to the apexes 108 form afilter element support portion 32.

One skilled in the art will appreciate that variances in the filterframe material(s), dimensions, geometry, and/or processing can all bemade to create alternate embodiments with varying desirable properties.For example, the relative position of the central collar 46 to theapexes 108 can be varied according to FIGS. 5C and 5D.

The frame (now at functional size and preferred geometry) was thenlightly coated with fluorinated ethylene propylene (FEP) powder (e.g.,FEP 5101, available from DuPont Corp, Wilmington, Del.) by firststirring the powder in a kitchen blender (Hamilton Beach Blendmaster)after the powder was mixed into a “cloud,” the frame was lowered intothe blender for approximately 5 seconds (enough time for FEP to build uponto the surface of the frame). The frame, coated with FEP powder, wasplaced in an air convection oven (Grieve Oven, The Grieve Corporation,Round Lake, Ill.) set at 320° C. for approximately one minute followedby air cooling to room temperature.

A typical filtering media was made by laser perforating one layer of athin, polytetrafluoroethylene (PTFE) membrane using a 10-watt CO₂ laser.The membrane thickness measured about 0.0002″ (0.005 mm) and had tensilestrengths of about 49,000 psi (about 340 KPa) in a first direction andof about 17,000 psi (about 120 KPa) in a second direction (perpendicularto the first direction). The tensile measurements were performed at 200mm/min. load rate with a 1″ (2.5 cm) jaw spacing. The membrane had adensity of about 2.14 g/cm³. The laser power and shutter time parameterswere adjusted to allow the laser to consistently create uniform 0.004″(0.1 mm) diameter holes in the membrane. The hole pattern geometry wasthen adjusted to create a pattern with uniform hole size, uniform holespacing, and uniform strength throughout the pattern. This perforatedpattern was then folded on itself and heat-sealed using a local heatsource (Weber soldering iron, EC2002M, (available through McMaster Carr,Santa Fe Springs, Calif.)) into a pattern which would result in aconical shape. The conical flat pattern was then trimmed with scissors,inverted, and mounted upon the FEP powder coated NiTi frame and attachedthough the application of localized heat (the heat causing the FEPcoating on the frame to re-melt and flow onto the surface of the filtersack thus providing a biocompatable thermoplastic adhesive).

A guide wire component was then inserted into the collar end of theframe and a small amount of instant adhesive (Loctite 401, LoctitieCorp, Rocky Hill, Conn.) was applied and dried to adhere and create asmooth transition from the guide wire to the outer diameter (OD) of theframe collar. One skilled in the art will realize that attachment of thefilter to the guide wire could be accomplished by adhesion, welding,soldering, brazing, a combination of these, or a number of othermethods. The resulting embolic filter is as shown and described abovewith respect to FIG. 1 et seq.

A further embodiment of the present invention is illustrated in FIGS.18A through 18C. In this embodiment the filter assembly 30 includes aframe 31 that is slidably mounted to the support wire 36. Thisattachment may be accomplished through a variety of means, including byproviding a collar 46 that is sized slightly larger than the supportwire 36 to allow the collar to move relative to the support wire when inuse. Stops 114 a, 114 b are provided on the support wire 36 to limit therange of relative movement between the filter assembly 30 and thesupport wire 36. Constructed in this manner, the filter assembly 30 hasexceptional longitudinal compliance relative to the support wire in thatthe support wire can freely move between the stops 114 withouttranslating longitudinal or rotational movement to the filter assembly.The full range of proximal and distal movement of the filter assembly 30relative to the stops 114 is shown in FIGS. 18B and 18C.

While particular embodiments of the present invention have beenillustrated and described herein, the present invention should not belimited to such illustrations and descriptions. It should be apparentthat changes and modifications may be incorporated and embodied as partof the present invention within the scope of the following claims.

1. (canceled)
 2. A medical device comprising: a frame that iscompressible and has a longitudinal axis, a periphery transverse to thelongitudinal axis, a proximal end defining a plane, and a distal end,the frame including a plurality of support struts extending from theperiphery toward the longitudinal axis of the frame, each of supportstruts having a curved shape and each of the support struts beinggenerally coplanar with one another; and a membrane coupled to theframe.
 3. The medical device of claim 2, further including a collardisposed about the longitudinal axis of the frame such that theplurality of support struts extend between the collar and the peripheryof the frame.
 4. The medical device of claim 3, wherein the collar islocated at the proximal end of the frame.
 5. The medical device of claim4, wherein the collar and the plurality of support struts are coplanar.6. The medical device of claim 3, wherein each of the plurality ofsupport struts is s-shaped.
 7. The medical device of claim 3, whereinthe periphery of the frame is defined by a plurality of peripheralstruts, the peripheral struts extending between the proximal and distalends of the frame.
 8. The medical device of claim 3, wherein theplurality of support struts are formed from a tube of shape memorymaterial cut to form the collar and the plurality of support struts. 9.The medical device of claim 3, wherein the medical device is a filter.10. The medical device of claim 3, wherein the medical device is anoccluder.
 11. The medical device of claim 3, wherein the membrane isconfigured to substantially obstruct fluid from flowing through themedical device.
 12. A medical device comprising: a frame having alongitudinal axis and including a collar, a plurality of curved supportstruts, and a support portion radially offset from the collar and havinga proximal end and a distal end, the plurality of support strutsextending from the proximal end of the support portion to the collarsuch that the collar is longitudinally aligned with the proximal end ofthe support portion and such that each of the support struts arecoplanar with one another; and a membrane coupled to the frame.
 13. Themedical device of claim 12, wherein each support strut is s-shaped. 14.The medical device of claim 12, wherein the plurality of support strutsand the collar are coplanar.
 15. The medical device of claim 14, whereinthe plurality of support struts are formed from a single piece ofprecursor material including a tube of shape memory material cut to forma single ring that defines the collar, the support portion, and theplurality of support struts.
 16. The medical device of claim 12, whereinthe support portion includes a second plurality of support struts, thesecond plurality of support struts extending between the proximal anddistal ends of the frame.
 17. The medical device of claim 12 wherein themedical device is a filter.
 18. The medical device of claim 12, whereinthe medical device is an occlusive device.
 19. The medical device ofclaim 12, wherein the membrane is configured to substantially obstructfluid from flowing through the medical device.